The Tunnel Diode rests inside a small cavity in the Teflon dielectricI own three of these and I have seen several other and none of them
have the tunnel diode inside the BNC connector. Wonder if that would
even be possible since one end of the diode goes to GND and the other
to the end of the three 1k resistors you mention. Inside the Teflon
dielectric in the BNC is a 43 ohm resistor. The tunnel diode is soldered
between a GND pin on the BNC connector and the junction of the 43 ohm
and the last 1k, close to but outside the BNC.